1. Field of the Invention
This invention relates generally to kitchen ventilation systems, and more particularly to a system for removing cooking fumes from the area adjacent a cooktop.
2. Description of the Prior Art
In the art of kitchen ventilation, there is a variety of equipment. Some terms commonly used are "hood", "ventilator", "exhaust duct", "exhaust fan", and "water wash ventilator". Such terms have meanings generally as follows:
Hood: Inverted box shape structure usually constructed of sheet metal, and hung above the cooking appliances. Lowest edge of box is at a minimum of 78 inches above the floor for operator head clearance. The components of the hood required by building codes include: Underwriters Laboratories (U.L.) labeled grease filters, grease drip tray located beneath grease filters and pitched for drainage of grease collected by the filters to a removable collection cup. Cup capacity is not to exceed one gallon. Light fixtures, listed for installation in a commercial grease hood, must be installed to produce a minimum of 70 foot candles of light at the cooking surface. Hoods, as an industry standard, must project horizontally beyond the vertical projection of the cooking appliance area a minimum of 6 inches on all open sides.
Ventilator: General shape is rectangular when viewed from the front and, when viewed from the side, similar to 45.degree. triangle with the right angle at the ventilator's highest point along the wall and the hypotenuse running from the ventilator's lowest point at the wall out and up to its highest point farthest out from the wall. The height of the ventilator above the floor is determined by the type of cooking appliances placed under the ventilator. Codes require a minimum of 24 inches from the top of the cooking surface to a maximum of 48 inches above the cooking surface to the bottom edge of the filters over char broilers. The components of the ventilator required by building codes include: U.L. labeled grease filters, a grease drip tray located beneath grease filters and pitched for drainage of grease collected by the filters to a removable collection cup. Cup capacity is not to exceed one gallon. Ventilator must project beyond the cooking appliances only enough to completely cover the length of the appliances. The ventilator width must be sufficient to come within 12" of the front of the cooking surface.
Exhaust Duct: pipe or enclosure usually welded to the top of either a hood or ventilator device and running vertically or horizontally up and out of the building. Ducts terminate at a powered exhaust fan.
Exhaust Fan: Motor driven or powered fan mounted to draw air exhausted through the device into and through the connecting duct system into the fan for discharge away from the building.
Water Wash Ventilator (U.L. designation--grease extractor): Constructed in the configuration of a hood or ventilator. The grease filters are replaced by an extraction chamber including baffles and fixed pipe loop with nozzles placed to wash the interior of the extraction chamber. The pipe system is connected to a remote control panel with time clock and other required safety and operating components. The removable grease collection cup is replaced by a drain connected directly to a building floor drain. All visible areas of the water wash hood or ventilator require the same type of manual cleaning described below.
Both the hood and ventilators described above are completely contained within the kitchen. Grease and smoke extracted from the cooking area through either device creates the need for cleaning of all components exposed to the exhausted smoke and grease, including the duct connecting the device to an exhaust fan mounted outside of the building. All sheet metal parts, grease filters, grease cups, light fixtures ducts and fans require this cleaning. Both the hood and the ventilator are mounted directly above the cooking appliances. In both, the grease laden filters and collection cups must be removed from the holding frames to be cleaned in a dishwasher or large soak sink. The remaining components must be cleaned where they are mounted. Since they are mounted directly above the cooking appliances, the cooking appliances must be covered or otherwise protected while the device is cleaned. The normal method for cleaning the device is hot water under pressure or steam from a steam generator. A canvas or plastic funnel must be constructed to capture and carry away to a floor drain, the water used in cleaning. The requirements for cleaning these devices tend to limit the frequency of cleaning, because the cooking appliances must be turned off. This is normally done after the restaurant closes, and requires at least one employee to stay after hours to monitor the cleaning crew and lock up after the cleaning is complete. Proper cleaning requires two or six or more hours, depending on system size and configuration. Therefore, complete cleaning is normally limited to one to four times per year. Meanwhile, grease filters, collection cups and exposed portions of the device must be cleaned more often. These removable accessories and exposed surfaces are cleaned as often as daily in most well run operations. This requires an employee to devise a way to get up to the filters and cups and into the device. Filters and cups must be removed, carried to wherever they will be cleaned, cleaned and then returned and replaced in the device. The exposed surfaces of the device are wiped down by hand. The ventilation system is typically the most difficult part of a building to clean other than the kitchen floor. The floor however requires only a mop and bucket, and can be mopped with the cooking appliances on or off.
Considering the foregoing, it is an object of this invention to provide a kitchen ventilating system that is easy to clean.
Further regarding prior art, conventional ventilators of the canopy or backshelf design mount above or beside the cooking appliances. Building codes require an air space between the cooking surface and the grease filter in the ventilator, for fire safety. Temperatures in excess of 1,200 degrees are present at the surface of some cooking appliances. Filters collect and hold grease extracted from the exhaust air. This accumulating grease presents a flash fire hazard at temperatures above 400 degrees. By providing the space required by the codes, cooler air from the room is drawn across the cooking appliance and into the ventilator to carry away the cooking by-products of grease and smoke, as well as the heat. The air space separating the cooking surface and the filter is there to facilitate a reduction in the cooking fume temperature as cooler room air is mixed with the cooking fumes as they move farther from the cooking surface.
A typical cooking surface is 36 inches or more above the finished floor. Codes require from 24 to 48 inches clearance above the cooking surface to the bottom edge of the grease filter in a canopy hood installation. Even with some specially designed grease filters, the minimum dimension is 16 inches. A typical hood or ventilator height dimension is 12-24 inches from filter bottom to top of ventilator. Adding the minimums of 12 inch hood height plus 16 inches minimum from the bottom of the grease filter to the top of the cooking surface and a cooking surface height of 36 inches above the floor, equals 64 inches of vertical wall space consumed and unusable.
Backshelf-type ventilators are desirable in many cases where it is desirable to serve food items over the top of a ventilator such as in cafeteria line, cook-to-order operations, and full service kitchens where the chef wants to face the person picking up or calling in food orders, while cooking. A minimum ventilator height of 64 inches such as mentioned above, is unacceptably tall for the chef to pass food over the top of the ventilator. In contrast, for an installation where the food is to be passed over the top of the ventilator, a ventilator top height of 47 inches is an acceptable height for pass-over operation.
It is therefore another object of this invention to remove fumes from the area adjacent a cooking surface and pass them through grease filters located a safe distance from the source of heat and flames but without consuming excessive kitchen wall or floor space, and still have the filters accessible for cleaning. It is a further object to reduce the overall height of the device for pass-over operation.
Referring further to the prior art, a fixed pipe water wash ventilator such as mentioned above, only cleans the extraction plenum. All surfaces exposed to view must be cleaned just like the conventional devices. The mechanics of the water wash system require professional maintenance. Lack of or improper service of the more complicated self cleaning feature, of conventional water wash ventilators, along with routine mechanical breakdowns, cause the self cleaning feature of these ventilators to be inoperable at times. The very nature of the term "self cleaning" implies that no physical check of the area to be self cleaned, is required. Therefore, problems often go undetected. It is also impossible in some designs, and very difficult in other designs, to manually wash the concealed extraction area when the self cleaning feature is inoperable.
Therefore another object of this invention is to provide a lower cost alternative to water wash extractors used in food service operations. It is also an object of this invention to provide a device that can be conveniently cleaned with a portable water spray system while allowing access, by the operator, to all areas of the ventilator and make all areas accessible for visual inspection.
Further referring to prior art problems, the building wall surfaces between the cooking appliances and the conventional devices must be cleaned, and become unusable space for anything that cannot be in direct contact with the grease and smoke laden exhaust air. The conventional ventilators and hoods hang into the room and consume wall and ceiling space. All interior space in today's food service buildings is at a premium. It seems that there is never enough space and it costs too much. Another object of this invention is to make wall space above the ventilator usable for storage shelves or other food preparation uses, and avoid use of floor space for the ventilator, so that cooking appliances can be placed directly against the face of the wall fronting the ventilator excepting allowances for utility connections at the appliances.
Another aspect of kitchen ventilation systems includes the exhaust duct and fan. Upblast spun aluminum exhaust fans are the standard for food service ventilation. The powered roof fan is placed on top of a roof curb. The curb supports the fan and is used for sealing the roof opening required to allow passage through the roof, of the duct which connects the roof fan to the ventilator inside the building. The fan pulls the grease laden air through the ventilator inside the building and through the connecting duct into the fan and then discharges out the top of the fan away from the building. All components of the system become coated with grease which gets through the grease filters and is carried in the exhaust air stream. The collected grease builds up inside all components. Only the fan is outside the building and exposed to the elements. The fan, by building code, must be open to the atmosphere, with no baffles or diverters that might be useful to deflect snow or rain, in the air stream. Therefore, rain water and snow can enter the top of the fan. The fan's design must keep the snow and rain out of the building and, therefore, drains this water out at the base of the fan. These drains allow the collected grease inside the fan to drain out. The rain water and snow also become contaminated with the grease collected inside the fan, and carry additional portions of the collected grease out of the fan to the roof. In addition, the wind bands on typical upblast grease exhaust fans are larger than the square base. Leaks occur at the assembly joints and assembly bolts around the wind bands. The top wind band must be removable for cleaning access to the fan wheel assembly. Being removable makes it virtually impossible to keep this joint leakproof. Roofing materials, whether treated paper and tar, or some newer membrane materials, are usually petroleum by product based. The animal and vegetable fats in the collected grease from the kitchen act as a sponge, drawing the oil by-products out of the roofing material. This drawing out leaves the roofing material dry and brittle. Cracking and roof leaks follow this drying out. Many membrane roofing suppliers will not warrant their materials against attack by grease from food service ventilation. So the deposits of grease on the roof are not only unsightly, but also are destructive to the roof. It is therefore another object of this invention to avoid roof deposits of grease from exhaust fans.